1. Field of the Invention
The present invention relates to a brake system for braking front wheels or rear wheels in a buggy which is used for traveling mainly on an unleveled ground, in particular, in a buggy including a differential driving shaft connected to a propelling shaft, a pair of left and right differential output shafts connected to left and right wheel driving shafts, respectively, a differential mechanism for distributing power to the left and right differential output shafts, while being driven from the differential driving shaft, and a reduction case which has the diferential mechanism accommodated therein and supports the differential driving shaft and the left and right output shafts.
2. Description of the Related Art
There are conventionally known brake systems in such type of buggies, including (1) one which has a multi-plate brake mounted between a differential driving shaft and a reduction case supporting the differential driving shaft to brake the differential driving shaft (see U.S. Pat. No. 5,673,776, and (2) another which has a drum brake mounted on each of wheels (for example, see Japanese Utility Model Application Laid-open No.61-152524).
The buggy is used in many cases to travel on an unleveled ground and hence, it is required that the brake system for the buggy be disposed with its level set as high as possible above the ground, so that it will not contact projections on the ground surface to the utmost. Dust-proof and waterproof properties capable of preventing the entering of the earth, sand and muddy water are also required and further, a cooling property enabling the brake system to withstand the severe braking is required. Of course, it is also necessary in stabilizing the braking attitude of the vehicle to be able to apply braking forces equally to the left and right wheels, regardless of the presence of the differential mechanism.
However, the multi-plate brake of the brake system (1) described above is on the differential driving shaft which is located at a relatively high level above the ground. Therefore, it is possible to ensure the level of the brake system above the ground, but because of an arrangement that the braking force is applied in a divided manner to the left and right wheel driving shafts by the differential mechanism, there may be cases wherein the braking force cannot be applied equally to both the wheels depending on a difference between the frictional resistances the left and right wheels receive from the ground surface. The drum brake of the brake system (2) must be formed at a large diameter in order to provide a large braking force and for this reason, it is difficult to ensure a level above the ground and moreover, it is necessary to provide special dust-proof and water-proof means for the structure of the drum brake.
Accordingly, it is an object of the present invention to provide a brake system in a buggy, wherein the problems associated with the conventionally known brake systems can be overcome, and all the above-described requirements and necessities can be satisfied.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a brake system in a buggy comprising a differential driving shaft connected to a propelling shaft, a pair of left and right differential output shafts connected to left and right wheel driving shafts, respectively, a differential mechanism for distributing power to the left and right differential output shafts, while being driven from the differential driving shaft, and a reduction case which has the differential mechanism accommodated therein and supports the differential driving shaft and the left and right output shafts, wherein the brake system comprises first and second brake shafts driven at increased speeds by the left and right differential output shafts, and first and second brakes capable of applying braking forces to the first and second brake shafts, respectively, the first and second brake shafts and the first and second brakes being disposed within the reduction case, such that the first and second brakes are cooled by lubricating oil in the reduction case.
With the above first feature, the first and second brakes are accommodated in the reduction case and hence, even during traveling of the buggy, it is possible to easily and reliably prevent the earth, sand and muddy water from entering into the brake system by the reduction case. Moreover, the first and second brakes can be cooled by lubricating oil in the reduction case, leading to an enhancement of the durability of the brakes.
In addition, the first and second brake shafts are driven at increased speeds from the left and right differential output shafts. Therefore, large braking torque can be applied to left and right front wheels with relatively small braking torques applied to the first and second brake shafts by the first and second brakes. In addition, it is possible to reduce the sizes of the brakes by reducing the loads on the brakes, and the level of the reduction case covering the brakes above the ground can be ensured to provide an excellent travelability of the buggy on an unleveled ground.
According to a second aspect and feature of the present invention, in addition to the first feature, each of the brakes is comprised of a plurality of rotary brake friction plates axially slidably retained on the corresponding brake shaft, a plurality of stationary brake friction plates superposed alternately on the rotary brake friction plates and axially slidably retained on the reduction case, and a brake actuator for urging the pluralities of rotary and stationary brake friction plates in an axial direction.
With the second feature, the load of each of the rotary and stationary brake friction plates can be reduced effectively. Therefore, the diameter of the brake device can be further reduced, and even if the first and second brake shafts are disposed in front and in the rear of the left and right differential output shafts, the level of the reduction case covering the brake devices above the ground can be ensured sufficiently.
According to a third aspect and feature of the present invention, in addition to the first feature, the first and second brakes are provided with a common brake actuator capable of actuating the first and second brakes with equivalent actuating forces.
With the third feature, equivalent braking forces can be applied simultaneously to the left and right wheels and moreover, the use of the common brake actuator can contribute to the simplification of the structure.
According to a fourth aspect and feature of the present invention, in addition to the second feature, the pluralities of rotary and stationary brake friction plates of the first and second brakes are disposed coaxially, and the brake system includes stationary pressure-receiving portions for receiving outer portions of the rotary and stationary brake friction plates, and a common brake actuator disposed between the rotary and stationary brake friction plates and capable of urging the rotary and stationary brake friction plates to the corresponding pressure-receiving portions with equivalent urging forces.
With the fourth feature, the pluralities of rotary and stationary brake friction plates of the first and second brakes can be clamped simultaneously by the single brake actuator, leading to a simplified arrangement.
According to a fifth aspect and feature of the present invention, in addition to any of the first to fourth features, the first and second brakes are disposed on a front side of the vehicle with respect to the left and right differential output shafts.
With the fifth feature, the lubricating oil stored in the reduction case is moved forwards by inertia and supplied in a large amount to the brake system upon braking during traveling of the vehicle. Thus, the brake system can be cooled effectively by the oil under the aid of travel wind, leading to a further excellent durability provided to the brake system.
According to a sixth aspect and feature of the present invention, in addition to any of the first to fourth features, the first and second brake shafts are disposed in parallel to the left and right differential output shafts, respectively, and coaxially with each other.
With the sixth feature, the first and second brakes can be accommodated compactly in the reduction case.
According to a seventh aspect and feature, in addition to the sixth feature, the diameters of the first and second brakes are smaller than the largest diameter of a reduction mechanism which interconnects the differential driving shaft and the differential mechanism.
With the seventh feature, it is possible to avoid the increase in size of the reduction case having the first and second brakes accommodate therein by reducing the diameters of the first and second brakes, thereby easily ensuring the level of the case above the ground.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.